Press

ABSTRACT

A press including a number of pairs of dies each clamped by a driving source to press set work pieces in a vertical direction, and a revolver holding the pairs of dies and rotatable around a vertical axis, wherein the revolver by rotating moves any pair of dies to a pressing position where pressing process is performed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 U.S.C. §371 national stage application ofPCT/JP2010/071391 filed Nov. 30, 2010, which is hereby incorporatedherein by reference in its entireties for all purposes.

TECHNICAL FIELD

The present invention relates to a press. More particularly, the presentinvention relates to a press clamping a pair of dies in the verticaldirection by a drive source and pressing process a workpiece set in thedies.

BACKGROUND ART

Japanese Laid-Open Patent Publication No. 2001-300780 discloses acurrently known press. This press clamps a pair of dies in the verticaldirection by means of a driving source to press a workpiece set in thedies.

SUMMARY OF THE INVENTION

In the prior art described above, however, in order to perform anotherprocessing step using a single press, dies must be removed from thepress for exchange, which takes some time and trouble. An object of thepresent invention is to provide a press in which the dies can beexchanged without removing them from the press in order to perform anumber of processing steps.

Embodiments of the present invention include a press including a numberof pairs of dies each clamped by a driving source to press a setworkpiece in a vertical direction, and a revolver holding the pairs ofdies and rotatable around a vertical axis, wherein the revolver byrotating moves any pair of dies to a pressing position where pressingprocess is performed.

This structure allows the press to hold in advance a numbers of pairs ofdies, to move any pair of dies to a position where pressing process isperformed simply by rotating the revolver. The dies may be thus changedwithout removing them from the press in order to perform a number ofprocessing steps.

Further, in the present invention, each time a pressing process iscompleted in one of the pairs of dies, the revolver rotates so that thepair of dies holding a processed workpiece is moved to a positiondifferent from the pressing position, and that another pair of dies ismoved to the pressing position.

This structure allows to perform processing using other pairs of dieswithout waiting for completion of transfer of processed workpieces.Therefore, it is possible to reduce time required for production andthus to provide a press with good production efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of the press.

FIG. 2 is a plan view of the press.

FIG. 3 is a side view of the press.

FIG. 4 is a schematic diagram with the transfer arms holding aworkpiece.

FIG. 5 is a schematic diagram with the transfer arm lifting up theworkpiece.

FIG. 6 is a schematic diagram with the workpiece taken out of the holderby the transfer arm.

FIG. 7 is a schematic diagram with the transfer arm placing theworkpiece in a pair of dies one stage above.

FIG. 8 is a block diagram showing a control system of the press.

FIG. 9 is a sectional view of the press taken along the line V-V of FIG.2 with dies (a) opened and (b) clamped.

FIG. 10 is a schematic plan view showing a part of the workpiecetransfer step of the first embodiment.

FIG. 11 is a diagram showing the flow of a workpiece transfer andassignment of the processing steps of the first embodiment.

FIG. 12 is a schematic plan view showing a part of the workpiecetransfer step of the second embodiment.

FIG. 13 is a diagram showing the flow of a workpiece transfer andassignment of the processing steps of the second embodiment.

FIG. 14 is a schematic plan view showing a part of the workpiecetransfer step of the third embodiment.

FIG. 15 is a diagram showing the flow of a workpiece transfer andassignment of the processing steps of the third embodiment.

FIG. 16 is a diagram showing the flow of a workpiece transfer andassignment of the processing steps of the fourth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

A first embodiment of the present invention will be described withreference to the drawings. FIGS. 1 to 3 respectively show a front view,a plan view and a side view of a press 10. As shown in FIG. 1, the press10 has a table 11 at the bottom, and a crown 12, an upper plate, at thetop. A crown 12 and the table 11 are tied with two vertical struts 13fastened by bolts. A rotation shaft 23, which will be described later,also functions as a strut, so that the crown 12 is virtually supportedby the rotation shaft 23 and the struts 13.

In the center of the press 10 is provided a revolver 20 rotatable abouta vertical axis. The revolver 20 has four holders 30 suspended from it.Each of the holders 30 supports three pairs of forming dies 40 a, 40 band 40 c in series. As shown in FIG. 3, below the top plate 111 of thetable 11, there is provided with a hydraulic cylinder 50 as a drivingsource of press, and a servo motor 60 as a driving source for rotatingthe revolver 20. As shown in FIGS. 4 to 7, the press 10 is providedwith, in addition to the above, a transfer device 70 as means oftransferring raw or processed materials (hereinafter collectivelyreferred to as workpiece W), hydraulic cylinder 50, and a control device80 which controls the servo motor 60 and the transport device 70.

Firstly the revolver 20 will be described in detail. In the top andbottom of the revolver 20 there is respectively provided with adisc-shaped upper plate 21 and lower plate 22, and in the center of therevolver 20 the rotation shaft 23 penetrating the center of the lowerplate 22 and upper plate 21. As shown in FIG. 3, above the upper plate21 a bearing 121 provided in the crown 12 receives a length of therotation shaft 23. Below the lower plate 22 a bearing 112 provided onthe top plate 111 of the table 11 receives a length of the rotationshaft 23. A pulley 231 is fixed on the lower end of the rotation shaft23. The whole revolver 20 is rotatable by a pulley 231 on the rotationshaft 23 driven by the servo motor 60. The lower plate 22 and top plate21 are supported by struts 24 near the periphery, away from thepositions of the holder 30.

The lower plate 22 has a number of cam followers 25 for the revolver 20to smoothly rotate on the top plate 111 of the table 11. Only four ofthe cam followers are seen in FIGS. 1 and 3. A spacer 232 is providedaround the rotation shaft 23 to secure such an amount of gap between thetop plate 111 and lower plate 22 of the table 11 that the cam follower25 may function. Portions of the lower plate 22 that are immediatelybelow each of the holders 30 suspended are separate lifting blocks 26,which may be lifted up when the cylinder rod 51 pushes up. As shown inFIG. 3, on the lower face of each lifting block 26 is provided a pair ofreceiving hook 261 having an inwardly bent L-shaped cross section. Thereceiving hook 261 on the lifting block 26 is configured to embrace fromaround the head 52 of the cylinder rod 51 when it rotates together withthe revolver 20 to come just above the cylinder rod 51 by.

The lower plate 22 is provided with foot receivers 27 fixed on the upperside, and each receiving a foot 341 provided at the lower end of eachtie rod 34 of each holder 30. Each foot receiver 27 is shaped so as tosupport the tie rod 34 to prevent it from any horizontal swing, but notto prevent its slight vertical movement during clamping as willdescribed below.

The upper plate 21 is provided with pairs of suspending hooks 28 fixedon the lower side at four positions in every 90 degrees, with two pairsfor hanging each holder 30. Each holder 30 has two pairs of T-bars 32fixed on the upper face, which are horizontally inserted in thesuspending hooks 28 on the revolver 20 so that the holder 30 issuspended. This structure makes the holders 30 exchangeable.

The dies 40 a, 40 b and 40 c and the holders 30 are now described. Eachholder 30 includes four die plates 31 a, 31 b, 31 c and 31 d. The T-bars32 mentioned above are formed on the upper side of the uppermost dieplate 31 a. As shown in FIG. 2, the die plates 31 a, 31 b, 31 c and 31 deach have two guide holes 33 in opposite ends, into which the tie rods34 are inserted through the four die plates 31 a, 31 b, 31 c and 31 d.The die plates 31 b, 31 c and 31 d, except the uppermost one 31 a, whichis fixed to the upper plate 21 of the revolver 20, may be slid up anddown while being guided by the tie rods 34. The die plates 31 a, 31 b,31 c and 31 d support separately the upper and lower dies of three pairsof dies 40 a, 40 b and 40 c as shown in FIG. 1. Each of the dies 40 a,40 b and 40 c may be exchanged by sliding horizontally.

Each of the die plates 31 a, 31 b, 31 c and 31 d has holes in the fourcorners, into each of which a suspension strut 35 composed of a longbolt is inserted. Each of the hanging struts 35 has four nuts (notshown) screwed thereon, which serve as stoppers defining the falling endof the die plates 31 b, 31 c and 31 d. The uppermost stoppers arescrewed at positions above the uppermost die plate 31 a so that thesuspension struts 35 are hung down from the uppermost die plate 31 a.The other stoppers are screwed at positions below the other die plates31 b, 31 c and 31 d to define the most lowered positions of the dieplates 31 b, 31 c and 31 d. For each holder 30, the position of thestopper can be adjusted to change the opening distance of a pair of dies40 a, 40 b and 40 c as desired, while the positions of the loweststoppers should be unified for all holders 30. Each of the dies 40 a, 40b and 40 c may be provided with the guide pins 41 on the lower die andas many opposed guide bushings 42 on the upper die, which may be used toalign the pair of dies when mounting.

Now the servo motor 60 and the hydraulic cylinder 50 will be described.As shown in FIG. 3, the hydraulic cylinder 50 is fixed on the lowersurface of the top plate 111 of the table 11. A cylinder rod 51 ispositioned upwardly from the hydraulic cylinder 50 through the top plate111 of the table 11 in order to transmit power of the hydraulic cylinder50. The cylinder rod 51 has a head 52 with an outwardly extending flangeformed at the end. A pulley 61 is fixed on the shaft of the servo motor60. The pulley 61 on the servo motor 60 is connected via a belt 62 tothe pulley 231 of the rotation shaft 23, so as to transmit rotationalforce to the rotation shaft 23.

Now the transfer device 70 will be described. As shown in the schematicdiagrams of FIGS. 4 to 7, the transfer device 70 includes four transferarms 71 provided at different levels, and each transfer arm 71 has aholder 72 at the end, which can hold a workpiece by suction. As shown inFIGS. 4 to 7, the transfer arms 71 are provided to allow to stretch ormove independently in the direction required of the front and back, upand down, and left and right. FIG. 4 shows the transfer arms 71 holdingthe workpieces W0, W1, W2 and W3. FIG. 5 shows the transfer arms 71lifting up the workpieces W0, W1, W2 and W3. FIG. 6 shows the transferarms 71 taking the workpieces W0, W1, W2 and W3 out of the holder 30 a.FIG. 7 shows the transfer arms 71 placing the workpieces W0, W1 and W2into the dies 40 a, 40 b and 40 c one stage above.

The control system of the press 10 will next be described. FIG. 8 is ablock diagram showing a control system of the press 10. The press 10includes a controller 80 as shown in FIG. 8. The control device 80controls hydraulic pressure in the hydraulic cylinder 50, rotation ofthe servo motor 60, and various movements such as listed above of thetransfer arm 71 of the transfer device 70.

A single pressing operation will next be described. FIGS. 9( a) and 9(b)is sectional views of the press 10 at the plane V-V of FIG. 2, withpairs of dies opened and clamped, respectively. As shown in FIG. 2, outof the four holders, one that has come just above the hydraulic cylinder50 at the time (hereinafter referred to as pressing position) is thetarget holder 30 for which a pressing operation is carried out. First,starting with the condition of FIG. 9( a), the hydraulic cylinder 50 iscontrolled by controller 80 to start pushing up the cylinder rod 51. Thelifting block 26 in the lower plate 22 of the revolver 20 is lifted upby the cylinder rod 51 rising, and then the lowermost die plate 31 d islifted up. The lifting block 26 has a wider upper surface than thecylinder rod 51, and thus allow a more stable lift as compared with thecase where the cylinder rod 51 directly raises the die plate 31 d. Then,the die plates 31 b and 31 c rise in turn, and each pair of dies 40 a,40 b and 40 c sandwiches respective workpieces W.

As shown in FIG. 9( a), there may be some play in the vertical directionin the hanging structure with the T-shaped bar 32 on the holder 30 andthe hanging hook 28 on the upper plate 21 of the revolver 20. Inaddition, there may be a gap of about 1 mm between the upper plate 21 ofthe revolver 20 and crown 12, when the dies are opened. With suchconditions, after all the workpieces W are sandwiched in the dies 40 a,40 b and 40 c, all the holder 30 are raised slightly and then the wholerevolver 20 is also lifted slightly. Accordingly, the dies 40 a, 40 band 40 c bear the load of the revolver 20 and all the holders 30, andthis weight thus presses to process the workpieces W. However, in casethat the largest processing weight required for pairs of dies 40 a, 40 band 40 c that is supported on the target holder 30 for press is greaterthan that total weight which the dies 40 a, 40 b and 40 c bear asmentioned above, the revolver 20 will rise into close contact with thecrown 12 and then the workpieces W will be pressed with an additionalreaction force applied from the crown 12.

In the condition of FIG. 9( b), the cylinder rod 51 next starts to drawback. The revolver 20 and the holder 30 fall by their own weight as thecylinder rod 51 goes lower. The die plates 31 b, 31 c and 31 d also godown in turn, and stop at the level where each gets in contact with therespective stopper on the hanging rod. Each pair of dies 40 a, 40 b and40 c opens to a preset distance when a single pressing operation forthis holder 30 is completed.

Now a flow of producing parts according to the first embodiment will bedescribed. FIG. 10 is a schematic plan view showing a part of theworkpiece transfer step according to the first embodiment. The transferdevice 70 is positioned in front of the press 10 as shown in FIG. 10 (a)to (d). This means that the position where transferring operations areperformed on the holder 30 (hereinafter referred to as transferringposition) is the same as the pressing position. FIG. 11 is a processdiagram showing flow of workpiece transfer and assignment of processingsteps according to the first embodiment. Plate materials such asaluminum plates or the like usually undergoes several processing steps,such as drawing, forming, punching and trimming, in sequence to producea specific kind of parts. In FIG. 11, symbols A1, A2, etc. appended toeach pair of dies represent different kinds of processing steps assignedto those pairs of dies. For example, A1 represents the first processingstep to produce a part A. The arrows drawn to the right of the holder 30a represents flow of workpieces W0, W1, W2 and W3. For example, W1represents a workpiece after completion of the first processing step forproducing parts A. Note that the W0 is a raw material before anyprocessing.

A flow of producing parts A using the press 10 will be described below.FIG. 10 (a) shows a condition in which the holder 30 a in pressingposition, the holder 30 b, the holder 30 c and the holder 30 d arrangedcounterclockwise in this order. Parts A requires three processing stepsA1, A2 and A3 to produce, which are assigned to the pairs of dies in theholder 30 a from bottom up in that order, as shown in FIG. 11. First,the hydraulic cylinder is controlled by a control device to perform apressing operation described above on the holder 30 a in the pressingposition as in FIG. 10( a). The workpieces W0, W1 and W2 respectivelybecomes workpieces W1, W2 and W3 via processing steps A1, A2 and A3, asshown in FIG. 11. The control device then drives the transfer arms 71into movement as follows. First, as shown in FIG. 4 and FIG. 10 (b), theupper three transfer arms 71 are inserted into the holder 30 a and takehold of the processed workpieces W 1, W2 and W3. At the same time, thelowermost transfer arm 71 takes hold of a raw material workpiece W0piled in the material storage M. The transfer arms 71 then lift up theworkpieces W0, W1, W2 and W3 and temporarily go back out of the holder30 a, as shown in FIGS. 6 and 10 (c). Next, as shown in FIG. 7 and FIG.10 (d), the lower three transfer arms 71 are inserted again into theholder 30 a and place the workpieces W0, W1 and W2 in the pairs of dies40 a, 40 b and 40 c. At the same time, the uppermost transfer arm 71takes the workpiece W3, which has gone through all the processing steps,to the outside of the press. An operational cycle for producing parts Ahas thus been completed. This cycle is repeated to produce parts A insuccession by the single holder 30 a.

Next, the flow for the production of parts B, C, and D will bedescribed. Parts B, C and D each require three steps to produce, likePart A. The production process for parts B, C and D are respectively andindependently assigned to the die holders 30 b, 30 c and 30 d that arenot in the pressing position, as shown in FIG. 10( a) to (d). The pairsof dies are arranged in the holders 30 b, 30 c and 30 d in such a waythat the three steps proceed from bottom up as shown in FIG. 11, likethe holder 30 a. A desired holder 30 b, 30 c or 30 d may be moved to thepressing position by the controller controlling the servo motor torotate the revolver 20. The holder 30 b, 30 c or 30 d that has beenmoved to the pressing position may be controlled in the same way asdescribed above for production of parts A, in order to produce parts B,C or D corresponding to that holder.

The first embodiment of the present invention has been described above.According to this embodiment, the four holders 30 a, 30 b, 30 c and 30 dare supported in advance on the rotatable revolver and arranged in therotational direction, any holder can be moved to the pressing positionsimply by rotating the revolver. The dies 40 may be easily exchanged bysimply rotating the revolver 20 without removing them from the press 10,in order to carry out multiple processes, and thus the press 10 issuitable for multi-production.

According to this embodiment, in each holder three pairs of dies arelined in series in the pressing direction. Therefore, it is possible tocarry out three pressing steps in a single operation at the same time.This allows to integrate a process for producing parts consisting ofthree steps in a single press 10.

Now a second embodiment of the present invention will be described. Theelements shown in FIGS. 1 to 8 are common to the first embodiment, andthus the description of them will be omitted. The flow of producingparts according to the second embodiment will be described. FIG. 12 is aschematic plan view showing a part of the workpiece transfer processaccording to the second embodiment. As shown in FIGS. 12( a) to (d), thetransfer device 70 is positioned on the left side of the press 10. Thatis, the transferring positions and the pressing position are differentfrom each other. FIG. 13 is a process diagram showing assignment of theprocessing steps and flow of workpiece transfer, according to the secondembodiment. W, X, Y and Z represent a workpiece in process of producingparts A, B, C and D, respectively.

A flow of producing parts A, B, C and D by using the press 10 will bedescribed. In FIG. 12 (a), the holder 30 a in the pressing position, theholder 30 b, the holder 30 c and the holder 30 d are arrangedcounterclockwise in that order. Parts A, B, C and D each require threesteps to produce. Production processes for these kinds of parts areassigned to different holders, as shown in FIG. 11. Steps A1, A2 and A3are assigned to the dies of the holder 30 a from bottom up in thatorder, and likewise processing steps for parts B, C, and D are assignedto the pairs of dies in the other holders 30 b, 30 c and 30 d frombottom up in order.

First, the hydraulic cylinder is controlled by a control device to carryout a pressing operation described above on the holder 30 a in thepressing position as in FIG. 12( a). The workpieces W0, W1 and W2respectively becomes workpieces W1, W2 and W3 via the processing stepsA1, A2 and A3, as shown in FIG. 11. During this pressing operation, atransferring operation is carried out on the holder 30 d as in FIG. 12(a). The holder 30 d holds workpieces Z1, Z2, Z3 which have gone throughsteps D1, D2, D3. At this time, the workpieces Z1 and Z2 for which notall processing steps are completed is transferred one stage up into dies40 b and 40 a, the workpiece Z3 for which all processing steps have beencompleted are taken out of the holder 30 d to the outside of the press10, and the workpiece Z0 which is a raw material before any processingis brought from a material storage M outside the press 10 into thelowermost pair of dies 40 c in the holder 30 d. During this, the controldevice drives the transfer arm 71 in the same movement as the transferarm according to the first embodiment described above. The servo motoris then controlled by the control device to rotate the revolver 20clockwise by 90 degrees. One operational cycle for production of partsA, B, C, and D has thus been completed.

Parts A, B, C and D may be produced in this order by repeating the cyclein which, as described above, a processing process is performed at thepressing position while a transferring process is carried out at anotherposition, and then the revolver rotates by 90 degrees. This cycle isrepeated to produce parts A, B, C and D in succession, by all theholders 30 a, 30 b, 30 c and 30 d.

The second embodiment of the present invention has been described above.According to this embodiment, after each pressing operation iscompleted, the revolver 20 is rotated, the dies holding the workpiecesthat has been pressing process is moved to a position different from thepressing position while another holder is moved to the press position.Therefore, it is possible to carry out processing steps in the dies ofanother holder, without waiting for the completion of transfer ofprocessed workpieces. Therefore, it is possible to provide a press withgood production efficiency and can reduce the time required forproduction. According to this embodiment, processes of processing partsA, B, C and D are completed in turn one by one. Assembly process ofparts may be started as soon as all kinds of parts are collected by onepiece for each kind, and this can contribute to an improved efficiencyin production process.

A third embodiment of the present invention will be described withreference to the drawings. The elements shown in FIGS. 1 to 8 are commonto the first embodiment, and thus the description of them will beomitted. FIG. 14 is a schematic plan view showing a part of workpiecetransferring process according to the third embodiment. As in FIG. 14(a) to (d), the transfer device 70 is arranged on the left side of thepress 10. Further, the transfer device 70 has transfer arms similar tothose shown in FIGS. 4 to 7. Unlike the first embodiment, however, thetransfer device 70 has two, left and right transfer arms 71 a and 71 bat each of three levels, as shown in FIG. 14( a) to (d). The total sixtransfer arms can independently hold a workpiece by a holder 72 providedon their end. FIG. 15 is a process diagram showing the flow of workpiecetransfer and assignment of processing steps according to the thirdembodiment. W, X and Y represent a workpiece during processing parts A,B and C, respectively.

A flow of producing parts A, B and C of the third embodiment will bedescribed. For FIG. 14 (a) shows a condition in which the holder 30 a inthe pressing position, the holder 30 b, the holder 30 c, the holder 30 dare arranged counterclockwise in this order. The kinds of parts A, B andC each requires four steps to produce. The production processes forthese kinds of parts are assigned to the lower, middle and upper rows ofdies respectively so that their final processing step belong todifferent holders. As shown in FIG. 15, the final steps for each part A,B and C fall in the holders b, c and d, respectively.

First, the hydraulic cylinder is controlled by the control device tocarry out a pressing operation described above on the holder 30 a in thepressing position as in FIG. 14( a). The workpieces Y0, X1, W2 becomesworkpieces Y1, X2, W3 through the processing steps C1, B2, A3,respectively, as shown in FIG. 14 (c). During this pressing operation,the transfer device is controlled by the control device to carry out atransferring operation on the holder 30 d. As shown in FIG. 14( a), theholder 30 d holds workpieces Y4, X1, W2 which has just gone through thesteps C4, B1, A2. The transfer arms 71 b on one side in the transferdevice 70 hold workpieces Y3, X0, W1 which are to be placed next. Out ofthese workpieces, the workpiece X0 is a raw material that was broughtfrom a material storage outside the press 10. The transfer device 70inserts the transfer arms 71 a into the revolver 20, as shown in FIG.14( b), and the transfer arms 71 a hold and lift up the workpieces Y4,X1, W2 in the dies of the holder 30 d. The transfer arms 71 b then placeand set the workpieces Y3, X0, W1 in the dies of the holder 30 d, asshown in FIG. 14( c). In condition shown in FIG. 14( c), transfer arms71 a are temporarily moved out of the revolver 20 while holding theworkpieces Y4, X1, W2. At the same time, the revolver 20 is rotatedclockwise by 90 degrees by the control device, reaching the conditionshown in FIG. 14( d). The workpiece Y4, as all the processing steps arecompleted, is transferred out of the press 10 by the transfer arm. Oneoperational cycle for producing parts A, B and C has thus beencompleted.

The above is a part of the production flow. The transfer devicebasically repeats a behavior in which it removes workpieces from pairsof dies by its transfer arms on one side, and place on the same pairs ofdies workpieces that has been held in the transfer arms on the otherside. The role of the transfer arms will alternate for every cyclebetween the left and right side. The workpieces are thus transferred inturn to neighboring die holders, as shown in FIG. 15. Some transfer armsare, though, differently moved when they remove the completely processedworkpieces W4, X4, Y4 to the outside of the press, or bring the rawworkpieces W0, X0, Y0 from a material storage outside the press. PartsA, B and C are produced in turn by repeating a cycle in which, asdescribed above, a processing operation is performed in the pressingposition, while a transferring operation is performed in anotherposition, and then the revolver is rotated by 90 degrees.

The third embodiment of the present invention has been described above.According to this embodiment, since the final steps of processing eachkind of parts A, B, and C are assigned to different die holders 30 b, 30c and 30 d, processes of processing parts A, B, and C are completed inturn one by one. Therefore, assembly process of parts may be started assoon as all kinds of parts are collected by one piece for each kind, andthis can contribute to an improved efficiency in production process.Further, according to this embodiment, there is no need of transferringworkpieces between upper and lower rows of dies. This allows transferarms to remain in the holder after they have removed the processedworkpieces until they place those workpieces to be processed next.

A fourth embodiment of the present invention will be described withreference to the drawings. The elements shown in FIGS. 1 to 8 are commonto the first embodiment, and thus the description of them will beomitted. As in the third embodiment, the transfer device 70 is disposedon the left side of the press 10. The transfer device 70, by two leftand right in each height of the four-stage, and has transfer arm 71 a ofeight books, 71 b. FIG. 16 is a process diagram showing the flow of theworkpiece transfer and assignment of the processing steps according tothe fourth embodiment. Workpiece W represent what in the processing stepof the component A.

A flow of producing parts A according to the fourth embodiment will bedescribed. Parts A require twelve steps to produce, and these steps areassigned to the pairs of dies from bottom up in order, four steps foreach row, as shown in FIG. 16. In the same manner as in the thirdembodiment, the press repeats the cycle in which a processing operationis carried out in the pressing position while a transferring operationis performed in another position and then the revolver rotates by 90degrees. The transfer device repeats a behavior that is basicallysimilar to the third embodiment in which it removes a workpiece from thedies by its one transfer arm while it places the workpieces held byanother transfer arm into the same dies. The transfer device, however,operates with an upward movement one stage above as in the firstembodiment, when it brings a raw workpiece W0 from outside of the pressinto the bottom stage of the holder 30 a and takes a workpiece W12 forwhich all processing steps are completed out of the top stage of theholder 30 d to the outside of the press. The workpieces W4 and W8 in theholder 30 d is replaced in the dies one stage above in the holder 30 a.Parts A are produced through the above process.

The fourth embodiment of the present invention has been described above.According to this embodiment, since all the twelve steps are assigned tothe twelve pairs of dies, a production process with twelve steps can beintegrated to a single press.

The embodiments of the present invention described above are forexemplary purpose only, and it should be meant that the presentinvention is not limited to that description. The number of holders 30hung on the revolver 20 is not limited to four and may be any plurality.Further, the number of pair of dies 40 held in one holder 30 is notlimited to three, but may be at least one. The number of dies held ineach holder 30 may be different from each other. Further, how to assignprocessing steps into pairs of dies is not limited to the embodimentsdescribed above, and a variety of arrangements may be envisaged.Behavior of the transfer device and the revolver may be appropriatelycontrolled by the control device 80 according to those arrangements.With this system, it is possible to integrate any production processincluding a number of processing steps within a single press 10.

In particular, the holder 30 that holds a number of pairs of dies 40,the stoppers may be adjusted on the suspension struts so that the dies40 held in that holder 30 have different opening amounts. Therefore, itis possible to effectively use the limited vertical space to assignprocessing steps, even if the heights of the workpieces W are differentwith each other. Furthermore, for the holder 30 for holding the dies 40a plurality of pairs, the weight required for a single pressingoperation may be suppressed to the largest processing weight that isrequired to pairs of dies. It is thus possible to save required energyas compared to clamping each pair of dies separately.

The number of the hydraulic cylinder 50 may be any plurality, while itwas one in the first to fourth exemplary embodiments. This means thatthere may be a number of pressing positions where pressing operationsare performed. With this arrangement, pressing operations can beperformed in parallel at a number of positions, which allows anincreased productivity. It should be noted that, when this configurationis applied to the first to fourth embodiments, control by the controldevice 80 and assignment of pressing positions are appropriatelydesigned so that the holder 30 which has gone through a pressingoperation at one press position may not undergo a further pressingoperation at another pressing position before any transferring process.For example, one more hydraulic cylinder may be provided in the oppositeof the hydraulic cylinder 50 shown in FIG. 2. Transferring operationsare performed at two positions other than a pressing position, and everytime the revolver 20 is rotated by 90 degree by the control device,transfer and press steps are alternately performed for each holder 30.

In the second to fourth embodiments, the position for transferringworkpieces W is not limited to the left side of the pressing position,but may be the right or opposite side. Alternatively, a number oftransfer devices 70 may be provided in some of those positions in orderto take partial charge of transferring process. This latter embodimentcan simplify the operation of each transfer arm 71 of the transferdevice 70. In addition, the number, shape and possible movement of thetransfer arms may be altered in accordance with the purpose of theembodiment. Transporting process may be manually performed by workers,while in the first to fourth exemplary embodiment it is done by thetransfer device controlled by the controller.

The hydraulic cylinder 50 may be arranged to downwardly clamps dies,while in the first to fourth embodiments it upwardly clamp dies 40. Inthis embodiment with downward clamping, it is required to providemembers such as springs which exhibits a restoring force to make theupper die to open. Further, the cam follower 25 may be provided on thetop plate 111 of the table 11, instead of the revolver 20.

1. A press comprising a number of pairs of dies each clamped by adriving source to press set workpieces in a vertical direction, and arevolver holding the pairs of dies and rotatable around a vertical axis,wherein the revolver by rotating moves any pair of dies to a pressingposition where pressing process is performed.
 2. A press according toclaim 1, wherein each time a pressing process is completed in one of thepairs of dies, the revolver rotates so that the pair of dies holding aprocessed workpiece is moved to a position different from the pressingposition, and that another pair of dies is moved to the pressingposition.